Standard risk factors for CHD and behavioral, psychological, socioeconomic and life situational factors will be studied in (a) 3,182 men in the Western Collaborative Group Study, (b) 275 pairs of twins and their single born sibs, (c) 300 families and (d) 2,655 postal employees with sharply different habitual physical activity. From these will be determined (1) average values in juveniles, (2) prevalence of CHD risk factors in normal environment, (3) determination of relative roles of genetic, familial, behavioral, psychological and environmental influences in the regulation of CHD risk factors, (4) comprehensive profiles of subjects exhibiting risk attributes and (5) comprehensive profile of coronary-proneness. The possible ability of enhanced physical activity to decrease the CHD incidence in Type A men will be determined. A new psychological questionnaire for the assessment of Behavior Pattern Type A will be developed. The relationship of Pattern A to CHD incidence will be delineated.